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BrianG · 07.17.2009, 03:24 PM

We kinda went over this before for the DX3r, but here goes anyway:

Wondering about "raw" 2s voltage, I emailed Spektrum. They said it would not like 7.4v, not to mention a fully "peaked" lipo is 8.4v. So, we're shooting for 6v to 6.5v MAX here.

Yeah, a switching BEC could be employed, but it will be about as efficient as a linear regulator on 2s. So, to get the switching BEC to be efficient, you need over 2s. Otherwise a linear regulator would actually be better. For example, a switch regulator is around 80% efficient at lower currents. Assuming the radio is drawing 200mA @ 6v, and the battery is 7.4v: That would mean a switching regulator would bes drawing 203mA from the battery. A linear regulator will only draw 200mA, so the linear one is actually more efficient on 2s.

To reap the benefits of high switching BEC efficiency, you need higher voltage, which means 3s+ is the minimum voltage. But, if the regulator goes out, that means the radio will receive the full 11.1v. The radio MAY survive 2s for a short time, but I doubt it will survive 11.1v. Another plus for the linear regulators; they are all but bulletproof. You really have to try to break one.

And, most any regulators of any kind need at least 0.5v (for LDO types) or 1.0v (for regular types) above the rated output to work right, which would be troublesome near LVC. To get around this, you could get a LDO style rated for 6v (or get an adjustable one and fix it at 6v), or a regular regulator like an LM7805 (5v).

Then, you need some kind of LVC/LVA, or some kind of indicator showing the voltage level of the actual battery.

So, after this is all said and done, it seems more trouble than it's worth. But, if you insist on using lipos, the best/safest/most efficient setup IMO is 2s using a 5v linear regulator with an LVA/LVC.

	(#24)
BrianG RC-Monster Admin Offline Posts: 14,609 Join Date: Nov 2005 Location: Des Moines, IA	07.17.2009, 03:24 PM We kinda went over this before for the DX3r, but here goes anyway: Wondering about "raw" 2s voltage, I emailed Spektrum. They said it would not like 7.4v, not to mention a fully "peaked" lipo is 8.4v. So, we're shooting for 6v to 6.5v MAX here. Yeah, a switching BEC could be employed, but it will be about as efficient as a linear regulator on 2s. So, to get the switching BEC to be efficient, you need over 2s. Otherwise a linear regulator would actually be better. For example, a switch regulator is around 80% efficient at lower currents. Assuming the radio is drawing 200mA @ 6v, and the battery is 7.4v: That would mean a switching regulator would bes drawing 203mA from the battery. A linear regulator will only draw 200mA, so the linear one is actually more efficient on 2s. To reap the benefits of high switching BEC efficiency, you need higher voltage, which means 3s+ is the minimum voltage. But, if the regulator goes out, that means the radio will receive the full 11.1v. The radio MAY survive 2s for a short time, but I doubt it will survive 11.1v. Another plus for the linear regulators; they are all but bulletproof. You really have to try to break one. And, most any regulators of any kind need at least 0.5v (for LDO types) or 1.0v (for regular types) above the rated output to work right, which would be troublesome near LVC. To get around this, you could get a LDO style rated for 6v (or get an adjustable one and fix it at 6v), or a regular regulator like an LM7805 (5v). Then, you need some kind of LVC/LVA, or some kind of indicator showing the voltage level of the actual battery. So, after this is all said and done, it seems more trouble than it's worth. But, if you insist on using lipos, the best/safest/most efficient setup IMO is 2s using a 5v linear regulator with an LVA/LVC.